DailyDirt: Long-Lasting Concrete Ideas

from the urls-we-dig-up dept

Every year, people pour billions of tons of concrete to build the stuff we live in and drive on. Concrete is everywhere, so it'd be nice to find better ways to make it and to make it more durable and to last longer. (FYI: Concrete is usually made up of 10-15% cement, and the cement is used to bind together sand and/or crushed rocks in concrete.) Here are just a few links on making better concrete.

Reader Comments

Superhydrophobic concrete would very likely make a horrible material for roadways, because hydrophobic materials tend to have one other thing in common: low friction. Which doesn't sound so bad until you realize that in the context of vehicles and roads, friction is more commonly known as traction, and surfaces that don't have much of it are called "slippery" in layman's terms.

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I recall hearing about Roman cement using animal fat and blood as surfactants. It ended up getting abandoned later on as pagan nonsense, which is pretty understandable actually. Since it does sound like superstitious sacrifices.

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w-e-l-l, the actual chemical process (called hydration), theoretically goes on forever (albeit in an asymptotic curve), as long as it has some water to do the reaction...but what you say is true: depending on the environment, concrete can be strengthened by proper 'curing' (so to speak), as far as keeping it moist over the first week or so...the other major problem, is that ignorant mud pushers mix in *way* too much water because it makes it easier to "pour" (concrete should always be "placed", not "poured", says my old concrete structures prof) and slop around the concrete, but causes weaker concrete in several ways: tends to segregate the aggregate, and makes the cement itself weaker...been all kinds of admixtures for a long time for specialized mixes: retardants to slow the reaction, accelerants (stop flagging real words, you useless spel czech) for quick-setting, fiberglass threads for strength and to increase its resistance to cracking, etc...oh, concrete WILL crack, just a matter of controlling it where you want it to crack...

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" not "poured", says my old concrete structures prof"

Very true. Also the time between mix and pour, temp, humidity....

I happened to go to a high school that had all sorts of testing equipment for my "Strength of Materials" course. Believe me when I say proper curing is extremely important to the strength and longevity of concrete. My concrete biscuits proved the point.

Re: Re: roman concrete

I saw something on the History Channel the other night (coincidentally, I was reading this page as it happened :D) that compared the strength of ancient vs. modern concrete and visited the likeliest source of their volcanic material in Italy. It also suggested an ancient text from a library still available today revealed the process, but I can't recall whether it went into detail on that matter or not (bad selective memory, bad!).